Abstract Gurson–Tvergaard–Needleman (GTN) model is a quite reliable tool that we can use to predict the failure of a component. Still, the determination of those parameters is not an easy task. It takes much time for computing, and sometimes we do find different sets of GTN parameters, with the same results after simulation. The purpose of this paper is to study how the change of the parameters affects the results, which means we are going to explore the non-uniqueness phenomena. We are going to conclude at the end, what are the main sensitive parameters.